Known in the art is a method of producing glass materials consisting in that a charge including the following ingredients (wt %): 47.6 SiO.sub.2, 29.6 Al.sub.2 O.sub.3, 15.8 Fe.sub.2 O.sub.3, 4.2 CaO, 0.6 MgO, 1.7 K.sub.2 O, 0.5 Na.sub.2 O is heated to a melting point temperature and melted in a graphite crucible, whereupon the melt obtained is slowly cooled (E. J. Deguire, S. H. Risbud. Journal of Materials Science, v. 19, N6 (1984) 1760-1766 "Crystallization and properties of glasses prepared from Illinois coal fly ash.")
The known method given a non-transparent material with a large content of iron (15 wt %) which substantially reduces the field of its application, particularly, makes it applicable only in construction industry and quite inapplicable in optical devices.
Known in the art is a method of preparation of glass materials from ash-slag waste having the following composition wt %:
______________________________________ CaO total 5.0-41.0 CaO unbound 4.0-13.0 SiO.sub.2 13.0-75.0 Al.sub.2 O.sub.3 5.0-26.0 carbon 1.0-2.0 Fe.sub.2 O.sub.3 1-24 MgO 2.0-6.0 Na.sub.2 O 0.1-1.0 K.sub.2 O 0.2-1.0 SO.sub.3 0.1-0.6 TiO.sub.2 0.2 ______________________________________
This ash-slag waste is the by-product of energy production using hard coal and brown coal.
In this method, a charge of this ash-slag waste is heated to a melting point in a reducing medium, whereupon the obtained melt is cooled by a thermal shock till a glass material is formed (Reprint of the Institute of physics of Siberian Division of the Academy of Sciences of the USSR, N 74, 1991 Krasnoyarsk, Pavlov V. F. et al. "A technique of Processing ashes, coals KATEK") herein incorporated by reference.
This type of ash-slag waste is difficult to reprocess due to its high calcium oxide content and presence of transient metals such as iron, manganese, chromium, titanium and others. The transient metals also limit the use of this waste material as a raw material for achieving transparent glass ceramic materials.
In the prior art, glass materials from all known ash-slag waste materials featuring comparatively low conductivity are used as heat-insulating materials. However, prior art methods fail to attain complete purification of the ash-slag waste being processed from impurities of transition metals, which to a great extent reduces the range of application of the glass materials since they can not be utilized in the manufacture of optically transparent glass materials.
As such, a need has developed to provide improved methods to obtain glass materials which are used for both for heat insulating applications and optical material applications. Responsive to this need, the present invention provides an improved method which overcomes the deficiencies in the prior art methods by the elimination of transient metal impurities and bonding of calcium oxide to form a glass material useful for insulating, wear resistance and optical material application.